根据C#中的用户输入解析为原始类型 [英] Parsing to primitive types, based on user input in c#

问题描述

我执行此操作的代码使用反射和给出的字符串，而不是用户输入.最终，我希望用户能够说"float""2.0"，并让计算机说，是的，这是计算机会说到的"float"或"bool""abc"，这是没有听说过的布尔值.

My code to do this uses reflection and strings that I give it, instead of user input. Ultimately I would like the user to be able to say "float" "2.0" and have the computer say, yeah, that's a float, or "bool" "abc" to which the computer would say, that's no boolean it's heard of.

将用户输入转换为原始类型名称就足够简单了，例如将"string"转换为"System.String"，将"float"转换为"System.Single"，等等.(尽管您知道的功能来做到这一点，那也很棒.)

It would be simple enough to take the user input and convert it to a primitive type name, like "string" to "System.String", "float" to "System.Single", etc. (although if you know of a function to do that, that would be great too.)

代码如下:

Console.WriteLine("1.0 => {0}", System.Single.Parse("1.0")); // this works fine.

Type t = Type.GetType("System.Single");              // for parsing floats
MethodInfo mi = t.GetMethod("System.Single.Parse");  // "ambiguous" if use "Parse"
object[] parameters = new object[] { "1.0" };
float f = (float)(mi.Invoke(null, parameters));     // get null exception here.
Console.WriteLine("Was succesfully parsed to: " + f);  

但是我在倒数第二行一直收到null异常.那里发生了什么事?

But I keep getting a null exception on the second to last line. What's going on there?

推荐答案

但是我在倒数第二行一直收到null异常.那里发生了什么事?

But I keep getting a null exception on the second to last line. What's going on there?

您的t.GetMethod不起作用.该方法称为Parse，而不是您编写的方法.它可能不再是模棱两可的-但这仅仅是因为它现在找不到任何方法并默默地返回null.

Your t.GetMethod doesn’t work. The method is called Parse, not what you wrote. It might no longer be ambiguous – but that’s only because it now finds no method and silently returns null.

要使呼叫明确，您需要指定期望的参数类型:

To make the call unambiguous, you need to specify the expected parameter types:

MethodInfo mi = t.GetMethod("Parse", new Type[] { typeof(string) });

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